Problem: $\begin{cases} f(1)=-7 \\\\ f(n)=f(n-1) + 3.5 \end{cases}$ $f(3)=$
Solution: ${f(2)}={f(1)}+3.5={-7}+3.5={-3.5}$ ${f(3)}={f(2)}+3.5={-3.5}+3.5={0}$ $f(3)=0$